Influence of stent height upon stresses on the cusps of closed bioprosthetic valves.

A finite element model of a bioprosthetic heart valve was developed to determine the influence of the stent height on leaflet stresses under various pressure loading conditions after valve closure. A nonlinear solution was used to obtain the stresses in the leaflets for stent heights of 14.6 mm, 19.0 mm and 22.0 mm respectively. The basic assumptions included an elliptic-paraboloid for a relaxed leaflet shape, a rigid stent, isotropic leaflet material property with a Poisson's ratio of 0.45, a uniform leaflet thickness and a stress dependent Young's modulus. The model predicted an increase of stresses on the closed leaflets as the stent height was reduced. This observation appears to mitigate, to some extent, the hemodynamic benefits thought to accompany the reduction of stent height of bioprosthetic valves.